Asking the question whether the mainstream media has a liberal or conservative bias is like asking whether al Qaeda uses too much oil in their hummus. I might think they use a little bit too much oil; some people might think it's a little dry. But the problem with al Qaeda is they want to kill us. And the problem with the mainstream media is that it has these other biases that are much more important.
I also focus on Bush and his administration - who do a lot of lying - and how a right-wing media has allowed them to get away with a lot of stuff that, in a different media environment, they probably wouldn't be able to get away with.